Fireproof Cable With Segmented Polyethylene Cladding

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Solution Overview

Problem

Cables with thick fire protection layers and polyethylene sheaths become bulky and difficult to handle while requiring high mechanical stability and fire resistance, with existing constructions prone to notch effects and mechanical failures due to film overlaps.

Innovation Solution

A cable design with a thin polyethylene cladding layer surrounded by a thicker fire protection layer, where the cladding layer's wall thickness can vary relative to the fire protection layer, and a metallic foil or metal sheath is used to enhance stability and prevent notch effects, allowing for a compact and stable structure with adjustable fire protection based on application needs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a relatively thick fire protection layer is applied to an already relatively thick polyethylene sheath, then fire resistance is improved, but the cable becomes too bulky, too heavy and/or difficult to handle

Engineering Contradiction:
Improvefire resistanceVSAvoidcable weight
Core Design Contradiction:
ReliabilityVSWeight of moving object

Solution Approach 1:

The cable sheath is segmented into multiple functional layers: an inner polyethylene sheath for mechanical stability and water protection, and an outer fire protection layer for flame resistance. This segmentation allows each layer to be optimized for its specific function without requiring excessive thickness in either layer, thus reducing overall cable weight while maintaining both mechanical stability and fire resistance.

Inventive Principle:
Principle #1Segmentation

2Reliability

If a relatively thick fire protection layer is applied to an already relatively thick polyethylene sheath, then fire resistance is improved, but the cable becomes bulky and difficult to handle

Engineering Contradiction:
Improvefire resistanceVSAvoidease of handling
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The cable sheath is segmented into multiple functional layers: an inner polyethylene sheath for mechanical stability and water protection, and an outer fire protection layer for flame resistance. This segmentation allows each layer to be optimized for its specific function without requiring excessive thickness in either layer, thus reducing overall cable weight while maintaining both mechanical stability and fire resistance.

Inventive Principle:
Principle #1Segmentation

3Reliability

If a film is provided radially inside the cable outer sheath as a vapor or liquid barrier, then water protection is improved, but notch effects can act on the outer cable jacket from the inside causing it to break or tear

Engineering Contradiction:
Improvewater protectionVSAvoidcable jacket strength
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The polyethylene sheath acts as an intermediary layer between the internal film barrier and the outer fire protection layer. This intermediate polyethylene layer absorbs and distributes the notch effects generated by the overlapping film, preventing these concentrated stresses from reaching and damaging the outer cable jacket, thus maintaining both water protection and structural integrity.

Inventive Principle:
Principle #24Intermediary (Mediator)

4Stability of the object's composition

If the wall thickness of the polyethylene sheath is increased to improve mechanical stability, then cable stability is improved, but the cable becomes bulkier and heavier

Engineering Contradiction:
Improvecable stabilityVSAvoidcable weight
Core Design Contradiction:
Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

The cable sheath is segmented into multiple functional layers: an inner polyethylene sheath for mechanical stability and water protection, and an outer fire protection layer for flame resistance. This segmentation allows each layer to be optimized for its specific function without requiring excessive thickness in either layer, thus reducing overall cable weight while maintaining both mechanical stability and fire resistance.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP3721455B1Cable with a fireproof layer
Publication Date: 2021.10.20 ABB KABEL UND DRAHT GMBH
  • EP3721455B1 patent drawingFigure 1
  • EP3721455B1 patent drawingFigure 2a~2b
  • EP3721455B1 patent drawingFigure 3

AI summary

A cable for laying in the ground, outdoors, in pipes or buildings, comprising a cable core (K) and a sheath which surrounds the cable core (K), wherein the sheath has a casing layer (12) and a flame-retardant and/or fire-retardant fireproof layer (13) and wherein the casing layer (12) and the fireproof layer (13) are coextruded, is to be specified in respect of the problem of a cable for laying in the ground, outdoors or in pipes but also in buildings, which cable, given a compact construction, is as stable as possible to mechanical actions and nevertheless exhibits as high a degree of resistance as possible in the event of fire, characterized in that the wall thickness (12a) of the casing layer (12) is, at least in sections, smaller than the wall thickness (13a) of the fireproof layer (13) which surrounds the casing layer (12), wherein a foil (9) is provided in a manner situated radially within and on the other side of the casing layer (12) and the fireproof layer (13), which foil has an overlapping region (11), or wherein a metal casing (7a) is provided in a manner situated radially within and on the other side of the casing layer (12) and the fireproof layer (13).